1. Field of the Invention
The present invention relates to an antifalsification document having a security thread embedded within the document.
2. Description of the Related Technology
To increase the antifalsification quality of security paper, identification cards, documents, etc., one of the security features known is to incorporate therein a security thread. In the case of paper products, the thread is introduced, for example, into the furnish layer as it is being formed during the manufacture of the paper, while in the case of multilayered synthetic products it is embedded between two individual layers. Such security threads may, for example, be compounded with mechanically testable additives (German "offenlegungsschrift" No. 16 96 245) or have certain optical properties, such as coloration that differs in transmission and reflection (German "offenlegungsschrift" No. 27,43 019).
It is also known to print writing, for example, on security threads. Lengths of film are first printed and then cut into strips. Since it is very difficult to cut the film so as to register exactly with the printed pattern, the distance between the individual areas of writing and the width of the threads are selected in such a way that one area of writing is at least always completely located on the cut thread (German "offenlegungsschrift" No. 14 46 851).
Further , it is also known to provide documents with security threads having an optically varying structure, such as a diffraction grid (German Pat. No. 25 55 214, German "offenlegungsschrift" No. 30 18 238).
Thus, the antifalsification document contains a feature that cannot be imitated in this form by photographic reproduction or copying techniques.
The known protection means have proved to be disadvantageous in that they are testable either only mechanically or only under special lighting conditions, that the optical effects can be detected by a viewer only very weakly, only using aids or even only if the viewer is an expert. In many cases it thus suffices to equip forged documents with simple lower-quality plagiarisms to simulate authenticity. Such threads are therefore less suitable as authenticity features capable of being easily tested visually.